"Dr. just called with blood test results," the 49-year-old wrote. "Have West Nile. Ugh. I'm fine, just tired. Takes a year to recover."

Whelchel recently finished competing in the reality series Survivor: Philippines, though it's unclear if she may have contracted the mosquito-borne disease there. West Nile Virus, once considered a minor threat to humans, is now now endemic in Africa, Asia, Australia, the Middle East, Europe and in the United States. In 2012, there were over 5,000 cases in the U.S alone.

"I just progressively worsened -- couldn't eat, couldn't drink," Mike Clark, a North Texas doctor, recently told NBC News regarding his experiences with the virus. "I got nauseated and finally had lost 26 pounds. It was, it was definitely scary. I mean, I didn't know if I was going to get better or worse."

According to the Mayo Clinic, symptoms of West Nile can include fever, headache, body aches, fatigue, skin rash, swollen lymph glands, and eye pain. There is no vaccine and no specific treatment.

"I've been very touched by all the sweet tweets," Whelchel added. "Other than tired, I'm feeling fine & expecting a full recovery. So grateful for you. Thanks!"